This disclosure relates to electrostatographic systems and more particularly to manifolds for toner collection and contamination control in electrostatographic process developer housings.
The disclosed manifold can be used in the art of xerographic, electrophotographic or electrostatographic printing. Generally, the process of electrophotographic printing includes sensitizing a photoconductive surface by charging it to a substantially uniform potential. The charge is selectively dissipated in accordance with a pattern of activating radiation corresponding to a desired image. The selective dissipation of the charge leaves a latent charge pattern that is developed by bringing a developer material into contact therewith. This process forms a toner powder image on the photoconductive surface which is subsequently transferred to a copy sheet. Finally, the powder image is heated to permanently affix it to the copy sheet in image configuration.
Two component and single component developer materials are commonly used. A typical two component developer material comprises magnetic carrier granules having toner particles adhering triboelectrically thereto. A single component developer material typically comprises toner particles having an electrostatic charge so that they will be attracted to, and adhere to, the latent image on the photoconductive surface.
There are various known development systems for bringing toner particles to a latent image on a photoconductive surface. Single component development systems use a donor roll for transporting charged toner to the development nip defined by the donor roll and the photoconductive surface. The toner is developed on the latent image recorded on the photoconductive surface by a combination of mechanical scavengeless development. A scavengeless development system uses a donor roll with a plurality of electrode wires closely spaced therefrom in the development zone. An AC voltage is applied to the wires detaching the toner from the donor roll and forming a toner powder cloud in the development zone. The electrostatic fields generated by the latent image attract toner from the toner cloud to develop the latent image. In another type of scavengeless system, a magnetic developer roll attracts developer from a reservoir. The developer includes carrier and toner. The toner is attracted from the carrier to a donor roll. The donor roll then carries the toner into proximity with the latent image.
One method of controlling toner emissions from developer housings in electrostatographic equipment is to relieve any positive pressure generated in the housing. Moving components such as the mag brush rolls and the mixing augers can pump air into the housing, causing slight positive pressures. These positive pressures can result in air flow out of the housing via low impedance leakage paths. This air escaping from the housing contains entrained toner and is a major potential source of dirt within the electrostatographic system. A common approach to relieving this pressure is through the use of a “sump sucker”. In its simplest form a sump sucker is a simple port into the air space above the developer material in the housing. This lowers the pressure in the housing below atmospheric pressure, therefore air flows into, rather than out of any low air impedance leakage paths within the housing. This toner laden air is drawn through a sump assembly. A shortcoming of these systems is that a considerable amount of toner emission contamination is present in the areas around the donor rolls in the developer housing. Additionally, excessive toner accumulation occurs on overhand trim features, and internal filtration is required to avoid excessive toner waste rates. The filtration operation results in frequent cleaning cycles to prevent clogging.
As electrostatographic printer process speeds increase, a corresponding increase of development roller angular velocities is required to maintain adequate developability or donor reload. The problem with escaping toner has become more acute and under these conditions toner emissions have increased and are considered a serious problem. Thus, merely having a vacuum source coupled to the housing has proven to insufficiently address the escaping toner issue. Therefore, it is a common practice to have the vacuum source connected to a manifold having an elongated opening adjacent either the location in which the toner cloud is created or adjacent the housing openings near the belt.
As mentioned above, the toner is airborne in a toner cloud during the transfer to the drum or belt. While most of the charged airborne toner adheres to the oppositely charged portions of the drum or belt, small amounts of the toner may remain airborne. The ability to control airborne toner has been a design issue in electrostatographic systems ever since toner was transferred to belts and drums by forming a toner cloud. One method adopted to control airborne toner in electrostatographic systems is to provide a dirt manifold for collecting the airborne toner that does not adhere to the transfer drum or belt. Such manifolds are often referred to as “dirt manifolds.”
Two main issues exist in the implementation of manifolds for developer housings. First is the issue of uniformity of flow at the inlet of the manifold which collects airborne particles of toner at the exit of the housing or from inside the housing. The second is the transportability of these particles through the manifold and the connecting tubes to the cyclone separator and the final filter.
Electrostatographic process developer housings include a manifold for control of toner emissions in electrostatographic systems. Current manifolds in use for toner emissions utilize airflow through the manifold to transport airborne toner. Current manifolds include center pull and single end pull manifolds (collectively referred to hereinafter as “single pull manifolds”). As used herein, the term “single pull manifold” refers to a manifold having a collection chamber, duct or region in fluid communication with an inlet and in fluid communication with a vacuum source through a single exhaust duct. Single pull manifolds have been designed to meet the transportability requirement. However, the current single pull manifolds may suffer from lack of uniform air velocity in the collection regions allowing some toner particles to escape into the machine cavity of the xerographic system.
Referring to FIG. 11, a prior art single pull manifold 1100 is shown. The manifold 1100 includes an elongated inlet 1102 extending between a first end 1104 and a second end 1106, a collection duct 1108, and an exhaust duct 1110. The collection duct 1108 and inlet 1102 are in contiguous communication along the length of the internal portion of the inlet 1102. The single exhaust duct 1110 provides the single pull feature as all toner entering the inlet 1102 flows through the inlet 1102 and a chamber of the collection duct 1108 to the single exhaust duct 1110.
Referring now to FIG. 12, the simulated performance of the prior art single pull manifold 1100 is illustrated. In FIG. 12, the position (mm) is measured from the first end 1104 of the inlet 1102 (position 0.0 mm) to the second end 1106 of the inlet 1102 (position −400 mm). The simulation was run utilizing a simulated prior art single pull manifold 1100 connected to a vacuum source providing an air flow of fifteen cubic feet per minute. The prior art manifold 1100 contains a cross member stiffening rib in the inlet slot 1102 about 175 mm from the first end 1104 of the inlet 1102 resulting in a discontinuity in the graph of the air flow velocity vs. position at that point. More importantly, FIG. 12 reflects that the prior art single pull manifold 1100 has a non-uniform air velocity along the length of the inlet 1102. FIG. 12 indicates that the magnitude of the velocity of air flow is substantially reduced near the first end 1104 and second end 1106 of the inlet 1102 as compared to the central portions of the inlet 1002. This reduction of air velocity near the ends 1104, 1106 of the inlet 1102 may result in airborne toner adjacent the ends 1104, 1106 of the inlet 1102 escaping the vacuum source. That escaping toner can become deposited on surfaces of the developer housing or escape the developer housing and enter the main housing of the print engine.
Therefore, an airborne toner collection manifold with improved air velocity uniformity in the collection region would be appreciated.
The disclosed manifold is a dual end-pull manifold having two streams of airflow at the collection region to improve airflow uniformity in the collection region of the inlet section. As used herein the term “dual pull manifold” refers to a manifold having a collection chamber, duct or region in fluid communication with an inlet and in fluid communication with one or more vacuum sources through a two distinct spaced apart exhaust ducts. Consequently, a “dual end-pull manifold” has the two exhaust ducts located adjacent opposite ends of the collection chamber.
According to one aspect of the disclosure, an airborne toner collection manifold for coupling in fluid flow communication with a vacuum source includes an inlet, a collection duct, a first exhaust duct and a second exhaust duct. The inlet defines a gap slot extending longitudinally between a first end and a second end. The collection duct is adjacent to the inlet and has a first end extending longitudinally at least to the first end of the gap slot of the inlet and a second end extending longitudinally at least to the second end of the gap slot of the inlet. The collection duct defines a cavity in fluid flow communication with the gap slot. The first exhaust duct is in fluid flow communication with the cavity of the collection duct and is configured to be coupled for fluid flow communication with the vacuum source. The second exhaust duct is in fluid flow communication with the cavity of the collection duct and is configured to be coupled for fluid flow communication with the vacuum source. The second exhaust duct is displaced from the first exhaust duct and is positioned relative to the first exhaust duct to be closer to the second end of the collection duct.
According to another aspect of the disclosure a development system that controls the emission of airborne toner particles generated during a development process in an electrophotographic printing process includes a housing and a manifold. The housing defines a chamber in which the airborne toner particles are generated. The manifold includes an inlet, a collection duct, a first exhaust duct and a second exhaust duct. The inlet defines a gap slot extending longitudinally between a first end and a second end. The collection duct is adjacent to the inlet and has a first end extending longitudinally at least to the first end of the gap slot of the inlet and a second end extending longitudinally at least to the second end of the gap slot of the inlet. The collection duct defines a cavity in fluid flow communication with the gap slot. The first exhaust duct is in fluid flow communication with the cavity of the collection duct and is configured to be coupled for fluid flow communication with the vacuum source. The second exhaust duct is in fluid flow communication with the cavity of the collection duct and is configured to be coupled for fluid flow communication with the vacuum source. The second exhaust duct is displaced from the first exhaust duct and is positioned relative to the first exhaust duct to be closer to the second end of the collection duct. The manifold is positioned relative housing to subject airborne toner particles to a suction at the inlet gap when coupled to the vacuum source.
According to yet another aspect of the disclosure an electrophotographic printing machine comprises a development system, a vacuum source and a manifold. The development system has a housing defining a chamber and is configured to generate airborne toner particles in the chamber during a development process in an electrophotographic printing process. The manifold is configured and positioned relative to the housing of the development system to control the emission of airborne toner particles generated in the chamber of the housing of the development system. The manifold includes an inlet, a collection duct, a first exhaust duct and a second exhaust duct. The inlet defines a gap slot extending longitudinally between a first end and a second end. The collection duct is adjacent to the inlet and has a first end extending longitudinally at least to the first end of the gap slot of the inlet and a second end extending longitudinally at least to the second end of the gap slot of the inlet. The collection duct defines a cavity in fluid flow communication with the gap slot. The first exhaust duct is in fluid flow communication with the cavity of the collection duct and the vacuum source. The second exhaust duct is in fluid flow communication with the cavity of the collection duct and the vacuum source. The second exhaust duct is displaced from the first exhaust duct and is positioned relative to the first exhaust duct closer to the second end of the collection duct.
Additional features and advantages of the presently disclosed toner collection manifold for an electrostatographic printer will become apparent to those skilled in the art upon consideration of the following detailed description of embodiments exemplifying the best mode of carrying out the disclosed apparatus as presently perceived.
Corresponding reference characters indicate corresponding parts throughout the several views. Like reference characters tend to indicate like parts throughout the several views.